A head-up display device (hereinafter referred to as “HUD device”) that projects an image onto a transparent plate member (a combiner or a windshield) disposed in front of a driver's seat to display the image superimposed on the view in front of the driver's seat as a virtual image has been known. The HUD device displays the image to be projected on a liquid crystal screen, and irradiates the liquid crystal screen with a light from a back side of the liquid crystal screen to project the image.
In the HUD device, because the image displayed to be superimposed on the front view needs to be clearly visible even during good weather, it is required that the image can be displayed with a sufficiently high luminance as the virtual image. To meet that requirement, the luminance of a light source for irradiating the liquid crystal screen with light from the back side may be increased. However, in that case, the amount of heat radiation of the light source increases, and a large space for housing the light source is required.
Under the circumstances, a technique in which the liquid crystal screen normally including three kinds of pixels of red pixels, green pixels, and blue pixels is configured by two kinds of pixels of red pixels and green pixels has been proposed (Patent Literature 1). With the above configuration, since the density of pixels that emit light on the liquid crystal screen per unit area can be increased, the luminance of the image displayed as the virtual image can increase even if the luminance of the light source does not increase.